How to Prevent Cracks in Drywallcomments (6) August 5th, 2011 in Blogs
Taping and finishing drywall is one of those things you can expect to do occasionally as a remodeler, but unless you're a full-time professional who does nothing but drywall you can also expect to run into problems once in a while. Such is the nature of the beast, and such is the experience of Howard, a general remodeler with years of experience.
He rates his drywall skills as intermediate, "by no means an expert," but he clearly isn't satisfied with a job that's amateurish in any way. The ceiling he has installed has developed two problems, as he describes in this post at Fine Homebuilding's Breaktime forum: a hairline crack 18 in. long on a joint, and a "bubble line" stretching 4 ft. to 5 ft. on a butt end that he swears wasn't there before he primed and painted.
He's used 1/2-in. drywall over joists 16 in. on center, with mesh tape and four coats of lightweight all-purpose joint compound.
"In my exerience with drywall I know that if the drywall has gaps at the seams the tape will bubble up but these seams are nice and tight," he writes. "Also, I put a light across the joint before I primed and it looked sweet. I am sort of a perfectionist and it is driving me crazy having these two issues."
Breaktime Business Forum
Questions about how the drywall was hung
At least one poster thinks 1/2-in. drywall is too skimpy for a ceiling. "Being picky, I'm surprised you used 1/2-in. on a ceiling," writes Tyr. "It should be 5/8-in., especially if [the ceiling is] textured," he adds, which makes drywall more susceptible to sagging.
But Liveonsawdust isn't so sure that's the issue. He says 3/4-in. drywall was once routine on ceilings, but adds: "I'm seeing more 1/2-in. lately. But we are using ceiling board (1/2 in.) that is much stiffer than regular 1/2 in. So I wouldn't worry about your 1/2-in. on 16-in. centers, especially with a smooth surface as opposed to a texture."
If there's no general agreement here, there's little doubt that Howard should have staggered the joints on adjacent sheets of drywall, something he says he did not do.
"Butt joints really should be staggered on walls and ceilings," writes Calvin. " More stress and movement on a continuous joint across several boards." That would explain why one of the defects Howard details could run more than 4 ft. where two butt ends meet. Staggered joints limit the length of a continuous crack.
While many of us would make sure that panel ends and edges landed on framing, where they could be securely fastened, Clewless1 offers an alternative.
"One trick I learned from the guy that did my house was to, in as much as possible, never let your butt joints end up on framing members," he says. "Best to let them 'float' and back them w/ e.g. a 3 in. scrap of plywood. This is good because: 1) you don't have to measure and fuss w/ getting a 4-ft. edge to be dead center; 2) fasteners near the edge often break the drywall which compromises the structure of the joint at that point; and 3) the floating joint is actually structurally superior. Movement of framing won't affect the joint and the joint is stronger because you don't have to put the fasteners so close to the edge.
"This makes it a piece of cake to layout a sheet w/out having to worry about having the joint line up."
posted in: Blogs, drywall, ceilings